The invention relates to an adjusting device for an airplane propulsion system of the type having a reciprocation piston combustion engine with an adjustable intake throttle valve and with a propeller pitch regulator.
Such an adjusting device is described in German Unexamined Published Patent Application (DE-OS) 33 06 612. This device serves, with a single control lever, to adjust the throttle valve of a piston cylinder motor and therewith the motor operation as well as the blade pitch of the propellers driven by the motor, respectively the effective propulsion force at the airplane. It is there provided, through pivoting of the control lever to continually completely open the throttle valve already in the lower rotational speeds of the motor and through further pivoting of the control lever with the help of a propeller regulator for the propeller pitch reduce the same from larger to smaller pitch in order that the motor rotational speed is increased from the range of 2300 revolutions per minute to 5000 revolutions per minute. In this rotational speed range the motor power output which is absorbed entirely by the propeller is adjusted exclusively through the rotational input to the propeller regulator. The control lever effects or works on the throttle valve with this control arrangement via several linkage connections and intermediate levers whereby the adjustment because of the unavoidable linkage play or tolerances can be achieved only somewhat imprecisely. Furthermore, this linkage mechanism has the disadvantage that the throttle valve goes to the closing position upon breakage of an intermediate member causing consequent idle running of the motor and an acute danger that the airplane might crash.
An objective of the invention is to provide an adjusting device of the above mentioned type with constructively simple means with the motor operation being precisely adjustable and also so that upon a breaking of an intermediate member the full motor operation and propulsion forces are provided to the airplane.
This objective is achieved according to preferred embodiments of the invention by providing an adjusting apparatus which includes a movable connecting rod linked to the throttle valve and movably guided in a relatively fixed rod casing, a throttle valve spring continuously biasing the connecting rod toward an open throttle position, a manually releasable blocking device for selectively blocking movement of the connecting rod with respect to the rod casing, and a carrying rod connected to the connecting rod for movement therewith and also connected at a control member of the propeller pitch regulator via the interposition of a further pitch regulator spring member.
When a connecting rod including a control knob operable by the airplane pilot is directly linked at a throttle valve lever and simultaneously a carrier rod is linked to the connecting rod for operating an adjusting lever for the propeller pitch of the propellers, there is permitted in a simple manner an exact and functionally certain adjustment of the motor operation and the torque of the propellers. Because an auxillary spring operates on the throttle lever in the opening direction, upon breaking of a member of the adjusting device, the throttle valve is fully opened and the motor performance is maintained.
In especially preferred embodiments of the invention a commercially available adjusting cable is used for the connecting rod, including a cable casing or housing surrounding and guiding longitudinal movement of a metallic cable core whereby the control knob operated by the pilot is connected with the cable core. Such adjusting cable is provided centrally of the control knob with a blocking knob by means of which the blocking of the cable core with respect to longitudinal displacement may be selectively disconnected.
In certain preferred embodiments, connecting pivot joints are arranged at the throttle valve lever and the adjusting lever for the propeller pitch so that the respective ends of the connecting rod and the carrier rod protrude through the respective connecting pivot joints. The ends of the cable core and the carrier rod are provided with abutment rings which are movable into abutment at the connecting pivot joints to effect respective pivotable movement of the adjusting lever and throttle valve lever.